1. Field of the Invention
The present invention relates to an inkjet recording ink, an inkjet recording inkjet recording ink set, and an inkjet recording apparatus.
2. Description of the Related Art
When a pigment is used in an inkjet ink or when a common hydrocarbon-based activator is used in an inkjet ink, it is difficult to achieve the same level of uniformity of image solid parts and color developing ability as is obtained using a dye-based ink.
Further, dye inks also have problems in that in the formulation of a dye ink for inkjet recording, if no surfactant is added, the surface tension of the ink is excessively increased as high as 40 mN/m, and the surface tension of the ink cannot be sufficiently decreased with only addition of a water-soluble organic solvent, and therefore degradation of uniformity of image solid parts results.
For this reason, attempts have been made to add a surfactant to an ink composition to reduce the surface tension of ink and improve the uniformity of image solid parts to thereby improve the color developing ability.
With use of surfactants that have been conventionally used, an effect of reducing the surface tension of ink can be expected, however, it is not effective for improving image quality in terms of reducing white spots, color bleed, etc. The surface tension of the resulting ink may be decreased, however, the ink may have high foamability as an ink, and thus this adversely affects ink-filling properties and discharge stability.
Therefore, use of an anti-foaming agent containing silicone oil or silica causes degradation of storage stability of the resulting ink, and the ink adheres on a nozzle internal wall, leading to discharge failure.
To solve the above-mentioned problems, Michihiko (JP2006-316243) disclosed an ink containing a fluorine-based surfactant having a specific structure in its ink composition, in view toward improving the image quality and obtaining low frothing and high discharge stability of ink. According to the proposal, the image quality is improved, and it is effective in improving low-foaming property and discharge stability.
However, the fluorine-based surfactant having the following Structural Formula (II) described in JP2006-316243 has low foaming and sufficient discharge stability, but is poor in image quality, particularly in color developing ability, and thus the ink is insufficient to ensure an effective enhancement of color developing ability.

In Structural Formula (II), Rf represents CF3 or CF2CF3, n is a positive integer of 1 to 4, m is a positive integer of 6 to 25, and p is a positive integer of 1 to 4.
Therefore, it has been required to immediately provide an inkjet recording ink which enables reducing white spots and color bleeding, forming high quality images, ensuring low foaming property and improving the discharge stability and its related properties.
The present invention aims to solve the above-mentioned conventional problems and to achieve the following object. That is, an object of the present invention is to provide an inkjet recording ink which contains a fluorine-based surfactant having a specific structure and which enables reducing white spots and color bleeding, forming high quality images, ensuring low foaming property (foamability) and improving the discharge stability in spite of exhibiting especially high color developing ability. Other objects of the invention include an inkjet recording ink set containing the improved ink, and an inkjet recording apparatus containing the improved ink.